Alloy of high surface stability comprising nickel and silicon



Patented M ay 2O, 1930 UNlTEDpS TA TES PATENT orrlcs PERCY A. E. ARMSTRONG, OF LOI IDONVILLE, AND RALPH 1?. DE VRIES, 0'5 NEWTON- VILLE,'NEW YORK, ASSIGNORS, BY DIRECT AND MESNE ASSIGNMENTS, TO L'U'DLUM STEEL COMPANY,OF WATERVLIET, NEW YORK, A. CORPORATION OF NEW JERSEY ALLOY OF HIGH SURFACE STABILITY COMPRISING NICKEL AND SILIOON No Drawing.

Our invention relates to an alloy containing principally. iron, nickel, silicon and carbon, which .is resistant to formationof scale at high temperatures, as when-subjected t0 flame 'or hot gases or used as electrical heating elements, and is resistant to the action of acids, such as hydrochloric and sulfuric acid. Alloys in accordance with our invention are well adapted for a large number of uses, as, for example, a few of the many uses are valves for internal combustion engines, blades for steam and gas turbines, carburizing boxes, furnace muflles, covers for pyrometer couples, lead pots, acid containing vessels, apparatus to be used in contact with acids other than nitric acid, electrical heating elements, etc. 7

The addition of silicon to iron gives increased Stable surface properties roughly proportionate to the quantity of-silicon added, butas the quantity of silicon alloyed with iron is increased, .brittleness is increased. We have found thatwhen nickel is incorporated with iron. and silicon, the proportion of silicon" can be ,very considerably'increased and acorresponding highly stable surface material obtained. and atthe same time the brittlenesses which would re- 7 sult without the nickel is avoided or at least very substantiallyreduced.

WVe have found that in general in orderto get tough material, that is, material which can be bent to some extent without breaking,

the silicon that can be carried increases as the nickel is increased, up to about20% of nickel, that from about 20%to 40% of nickel there is little change in-the proportion of silicon that can be used, .and above about 40% of nickel the proportion of silicon can no longer be increased and in fact to get. desirably tough material silicon should be decreased somewhat as the nickel is increased.

\Ve have found that withany given pro-' 1094:, silicon about Application filed January 7,1921. Serial No. 435,706.

greater is the temperature which may be withstood without substantial oxidation or scaling.

For valves of internal combustion engines, one good example of material in accordance with the present invention contains: nickel about 5%, silicon about 2%, and carbon about .3075: with the principal portion of the remainder iron; and another good material for this purpose contains: nickel about 2% and carbon about 30%. Chromium about 23% is f advantage for valve material and may be used,

for example, in valve steel of the compositions aboverefcrred to.

v For such purposes as carburizing boxes, lead pots, and the like, a material which gives long life at temperatures up to about 1800 F. may contain about 20% to 30% of nickel, and about 1% to 8.5% of silicon. A typical example of such "material is: nickel 227%, silicon 8.5%, carbon 3%, and the principal portion of the remainder iron.

The above typical analysis material for carburizing boxes will stand temperatures up to about 1800 F. which is about 150 to 200 higher than the temperature at which most ofthe carburizing Work is done. This material is tough and should be used in the cast condition. It can be heated to temper-.

atures substantially in excess of 2200 F. before becoming plastic, but at this high temperatureit is not highly resistant to scaling.

For withstanding very high temperatures, say up to about 2300? F. the nickel content should be increased and the iron and silicon reduced. For example 90% nickel, 5% silicon and 5%. iron may be used and such ma terial does not become plastic "until it reaches about 2375 F., and shows very little scaling at or towards such high temperatures. \Ve have found that some small percent-age of iron, say about 2% to 5% of iron,

appears to be necessary when the-nickel is high approaching 90% or over, for the nickel content is, of

I and silicon to melt tpgether and go into the alloy combination. se of such high nickel 4 course, quite expensive and unless the tem ratures to be withstood are excessively high: about to %.of1mckel with about 7% to 8.5% of silicon is preferabl used.

ere the conditions are such that me- I chanical stren his of relatively, decreased importance an brittlenessis notan impor tant objection the silicon content maybe mcrea sed while the nickel content is relative ly low, as for example an alloy containing: e

.nickel 15%, silicon 16%, carbon .2% and principal proportlon of the remainder iron withstands temperatures up to about 2000 F. for lon periods without appreciable oxi-i con combination are not secured to anappreciable extent when the nickel is below about 5% and the silicon below about 2%. When the temperatures to be withstood are rela tively low, the alloy can be composed of the various constituents of substant1ally--the lower limits set forth herein. Where low nickel is employed and the maximum silicon vis alloyed therewith, the resulting alloy 1s 7 not tough'and has a tendency towards brittleness. The maximum operating ,tempera tures with a low nickel-higher silicon alloy can bemuch higher than the maximum operating temperatures with the same nickel conchanica 'mercial practice.

tent and a lower silicon content within the scope of our invention. With such lower silicon content the allo is extremely tough and can be readily ormed mechanically: either by hot or cold working, preferably hot workin Fo -material which is tobe meworked, as for example, to be used in the ro led condition, it is desirable not to have the nickel lower than about 5%- nor higher than and the silicon is preferably kept'not higher than 16%, with either the minimum or maximum nickel content.

The silicon with either the minimum or maximum nickel should not be lower than about 2%. The carbon of the alloy is preferably kept low and may vary from about .05% to about 1.5%. The specific examples given herein are oflow carbon content within Com- The material, generally speaking, has cater ductility and greater ivorkability with the lower carbon. For

cast'material it is not of such importance that the carbon be low, but for commercial 7 reasons the carbon'is preferably kept low in thecast material. If the carbon is kept very low, for example below .20%, this increases the cost of the alloy because of the substantially carbon free components reis 's'u stantially 1 Mild or commercial steel or about 35% car:

hon is referably'used for melting purposes;

the sihcon used as an alloy addition is preferabl in the form of ferrous silicon, which carbon free,land the nickel used in the a tained carbon free. There is, therefore, no' tendency to pick up carbon from the use of lower priced nickel or silicon and to get the carbon. ashigh as,1.5%, forexam 1e, which may be done if desired, requires t e making of carbon additions in the furnace with .re-;.

For the reasons stated the lower the carbon oy can be commercially obisulting increase-in the cost of manufacture." V

below about 15%, thegreater are thecosts andthe difiiculties incommerical production Y and above about 50% carbon there is no decrease and there maybe increase in the melting cost due to higher carbon in. the straight nickel-silicon-iron-carbon alloy. If other Y ferro-alloys are added containing substantial proportions of carbon, the production of material with higher carbon lowers the cost.

Various other materials may be added to the alloy, but the amount of silicon has to'be reduced to compensate for such additionsif a tough material is desired." It is not an advantage from the'point of view of economy to add various other alloying materials, as the silicon content of the alloy is one of its cheapest components and should not be re- I placed it first cost is of importance. V

Chromium from about 2% to 15% may be added but when the. chromium is as high as 7% a ardening effect is noted which dimin ishes the quantity of silicon that can be used, so that it becomes undesirable to add more than this amount of chromium, particularly where strength is a requisite, since it adds to the cost unnecessaril and tends to increase brittleness of the al oy.- -As the chromium is increased there is a corresponding increase in the stable surface character of the. material, that is to say, resistance to rusting, staining and the like agents and to theaction of nitric acid. A very good stain resistin steel. is obtained with the addition to the al oy as above described of about 6% of chromium.

, In castin alloys of nickel-silicon-iron.

with low car on, there is avery high shrinking in the metal, particularly if the temperatures of casting are carried hi h, producing shrinkage cracks in thefinis ed castings. Therefore, it isdesirable, in commercial work, to add an additional alloying material to out down this initial shrinkage during casting and we have found that a low per- I centage of chromium is particularly good for this purpose. Any'other alloying material which will accoinplish the same end for'example, serves equally well without any detrlment to the properties of the alloy. 7

could be used in the place of chromium 1ow percentages of manganese such as 2% to 3%,

Where chromium is employed, we have found a good example for carburizing box work and articles of this character which have to be case hardened,- nickel about 22%, silicon about 7%, chromium from 1.5% up to about 7%, carbon about -.3%, and the principal proportion of the remainder iron.

Copper may be added to the alloy with the advantage that its addition does not require the reduction of the silicon to obtain material which is tough, and additions of from about .5% to about. 10% of copper may be made to advantage, giving the material increased life and resistance to oxidation, scaling, corrosion, erosion, and the like.

Manganese may be added in varying quantities from that naturally present in steel, say 15% to 1%, up to as high as about 6%. While it tends to embrittle the alloy and I to reduce the amount of silicon which can be used, very good material can nevertheless be made with manganese up to about 3%.

Aluminum may be used in this alloy conibination to replace part of the silicon but no material advantage as regards the resistance to scaling will be obtained and the'cost will be very much increased as will the melting difiiculties. For the purpose of electrical resistance elements it'may, however, be added with advantage. J

Zirconium can be added to the alloy composition but it does not seem to convey any addition to the valuable properties of the alloy. It increases melting diiliculties and has a tendency to produce unsoundness, particularly where the pouring temperature of the metal is high.

The higher melting point elements such as cobalt, tungsten, molybdenum, uranium and the like tendto detract fromthe toughness required for uses such as carburizing boxes, but these elements or combinations thereof, such for example as a combination ofcobalt and molybdenum may be used to replace corresponding amounts of nickel. or silicon or both in proportions not to'exeeed aftotal of about 3% without substantial adverse :efi'ect upon the hot oxidation properties. r

For electrical heating elements. silicon from about 2% to about 10% can be employed, and nickel from about 5% to about 90%. lVith the nickel about 90%, the silicon should not be more than 5% to 8%, since it is desirable that from 2% to 5% of iron should be present in order that the nickel and silicon may go into combination. The carbon shouldbe.under1%.*:

If the material is to be rolled or rolled and .drawn into wire, the silicon should preferably not be more than about 5%, but with cast electrical heating elements and the like sili-' con up to about 10% may be used.

The electrical resistivity of this alloy increases in general with increase in the amount of nickel and silicon employed, but depends j ing claims by which our more directly upon the amount" of silicon "than upon the amount of nickel, and electrical resistivity'of about 80 to 90 microhms per cubic centimeter can easily be obtained at about the middle of the range given above.

The following table gives some typical examples offde sirable analysis readily rolled into rods:

Chemical composition Electrical 7 resistance microhms C S 7 N1 Fe per cu. cm.

0.08 4.45 T60. 10 Theremainder I 75.5

0.10 52 48.74v .Theremainder 82.8

0.13 4.56 39.40 The remainder 92.5

acid and the like, but does not resist action V of nitric acid to any considerable degree.

For acid resistant materlals, carbon fimay be present up to about 1.5% for east articles,

Also carbon not to exceed about .5'% is preferably used for acid resistant articles to be subjected to rolling or other mechanical working treatment. The lower limit for silicon for such materials is about 5% and the upper limit about 12%. The lower limit of nickel is about 10% and the upper limit about 90%, as before.

One analysis well suited for acid resistant material was as follows: carbon .'1%, silicon 7%, nickel 22%, and the principal,part of the remainder iron. This alloy is strong and tough in the cast state and issuijzable to be made into various forms and articles, such as containers for acid, and is adapted for various articles required for use in contact with acid'materia'ls.

herein given are for the purpose of affording an understanding of our invention and not for limitation of the invention, the scope of the invention being'as set forth in the followinvention is defined. We claim: I

1. An alloy for resisting acidcorrosion and oxidation at high temperatures, containin g nickel in an amount greater than 20% and less than 60%, silicon inan amount greater than 3% and less than 9%, and the balance principally of iron.

2. An article resistant to corrosion and to It is' to be understood that the examples hot oxidation made from'alloyl' containing .as essential constituents nickel 8% to 60%,

silicon 2% to 10%, carbon under 1%, the remainder bein substantially entirely of iron.

3. An artic e resistant to corrosion and to hot oxidation madefrom alloy containing as essential constituents nickel 8% to 40%, silicon 2% to"10%, carbon under 1%, the" remainder being'substantially entirely of-iron; 1 4. An article resistant to corrosion and to hot oxidation made from alloy containing as essential constituents nickel 20%v to 40%, V

silicon 2% to 10%, carbon under 1%, the remainder being substantially entirely of 30 we have signed ournam'e's hereto.

PERCY A. E. ARMSTRONG. RALPH P. DE VRIES.

' Patent No. 1, 759, 477. H

CERTIFICATE or CORRECTION.

Granted May 20, 3.930, m

PERCY. A. E. ARMSTRONG ET AL.

It is hereby certified that error a I i I Wears P i t specification of th above numbered p tent requiring correction as follows: Page 3, line 4, fo -1h:

words "case hardened? read "cast"- and that th I I. j V c said LettersPatent should read with this correction therein that the same may conform tothe record o f the case in the Patent Office.

Signed and sealed this 24thday of June, A. 'D; 1930.

I (Set!) M- J- o Acting Commissioner of Patents. 7 

